Method and apparatus for controlling fuel supply shut off of an internal combustion engine

ABSTRACT

The invention involves stopping the operation of an internal combustion engine, when actual vehicle deceleration is detected after a vehicle deceleration operation. Alternatively, under conditions wherein it is possible to shut off fuel supply at the time of the deceleration operation, the invention involves stopping the operation of the engine by shutting off the fuel supply to some cylinders, and then shutting off the fuel supply to all cylinders when actual vehicle deceleration is detected. Since the fuel supply to the engine is timed to be shut off when the vehicle is decelerated, the speed is reduced smoothly without an accompanying large torque change. Thus, vehicle ride comfort and fuel consumption can be improved.

TECHNICAL FIELD

The present invention relates to a method and apparatus for controllingthe shut off of a fuel supply to an automotive internal combustionengine in a predetermined deceleration condition.

BACKGROUND ART

In general with automotive internal combustion engines (see for examplethe disclosure of Japanese Unexamined Patent Publication No. 63-179150)a mechanism is provided for shutting off the fuel supply in apredetermined deceleration condition.

With initial designs, the fuel supply is timed to be shut offimmediately after satisfying conditions such as, the rate of reductionin throttle valve opening exceeds a predetermined value, and the enginerotational speed at the start of the deceleration operation exceeds apredetermined value.

In reality however, a delay occurs from the start of the decelerationoperation until the engine output torque is reduced and the reduction intorque transmitted to the axle through the transmission to give anactual reduction in the vehicle speed. Therefore, if the fuel supply toall of the cylinders is shut off immediately after the decelerationoperation, then this will give a large deceleration resistance while thetravelling inertia of the vehicle is still large, resulting in a largetorque shock with deterioration in comfortable ride.

It has thus been considered to shut off the fuel supply after apredetermined time lapse from commencement of the decelerationoperation. Also, since an excessive torque change results when the fuelsupply is shut off to all cylinders simultaneously, then a generalstepwise fuel supply shut off control has been proposed to give stepwisereduction in the torque. This involves first shutting off the fuelsupply to some cylinders after the deceleration operation and thenshutting off the fuel supply to the remaining cylinders. With thisarrangement however, the timing for the fuel supply shut off to some orall of the cylinders is set according to an elapsed time after thedeceleration operation.

With the system wherein the timing to reduce the torque is merely setaccording to an elapsed time after the deceleration operation, it is notpossible to shut off the fuel supply with good timing. This is becausedeceleration conditions differ due to such factors as the engineoperating conditions at the time of or after the deceleration operation,and the travelling road surface conditions. This results in problemssuch as excessive torque fluctuations which detract from comfortableride, and the negation of any sufficient improvement in fuel consumptiondue to the delay in supply shut off.

In view of the above heretofore encountered problems, it is a firstobject of the present invention to provide a method for controlling thefuel supply shut off of an internal combustion engine which sufficientlyimproves fuel consumption and comfortable ride, by controlling the fuelsupply shut off on the basis of actual vehicle deceleration conditions.

Moreover, it is a second object of the present invention to provide anapparatus for controlling the fuel supply shut off of an internalcombustion engine which sufficiently improves fuel consumption andcomfortable ride, by controlling the fuel supply shut off on the basisof actual vehicle deceleration conditions.

DISCLOSURE OF THE INVENTION

In order to achieve the above objectives, the method and apparatusaccording to the present invention for controlling a fuel supply shutoff of an internal combustion engine involves the method and apparatusas indicated by the full lines in FIG. 1 for controlling a shut off of afuel supply to an automotive internal combustion engine at the time of apredetermined deceleration condition, and comprises: a vehicledeceleration detection step or device for detecting a vehicledeceleration condition which occurs with a delay after a decelerationoperation of the driver, and a fuel supply shut off step or device forshutting off of the fuel supply to the internal combustion engine when avehicle deceleration is detected by the vehicle deceleration detectionstep or device.

With such a construction, after the driver carries out a decelerationoperation, a delay occurs from the start of the deceleration operationuntil the engine output torque is reduced and the reduction in torquetransmitted to the axle through the transmission to give an actualvehicle deceleration.

The vehicle deceleration detection step or device detects the actualvehicle deceleration by detecting an axle torque change, or in the caseof a vehicle fitted with an automatic transmission incorporating atorque converter, by detecting the ratio or difference between input andoutput rotational speeds of the torque converter.

Since the fuel supply to the engine is timed to be shut off by the fuelsupply shut off step or device when the vehicle is decelerated, thenvehicle deceleration can be carried out smoothly without an accompanyinglarge torque change.

Furthermore, as shown by the dotted line in FIG. 1, the construction maycomprise, the beforementioned deceleration detection step or device, afuel supply shut off judgement step or device for judging if fuel supplyshut off is possible, and the beforementioned fuel supply shut off stepor device for shutting off the fuel supply to some of the cylinders whenit is judged by the fuel supply shut off judgement step or device thatfuel supply shut off is possible, and for shutting off of the fuelsupply to the remaining cylinders when a vehicle deceleration isdetected by said vehicle deceleration detection step or device.

With a device incorporating such a fuel supply shut off judgement stepor device, when initially judged that fuel supply shut off is possible,the fuel supply to some of the cylinders is shut off. Then when avehicle deceleration is detected, the fuel supply to the remainingcylinders is shut off. As a result, the fuel supply shut off is carriedout in a stepwise manner so that torque changes become smaller and thevehicle can be decelerated more smoothly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the structure and functions of thepresent invention.

FIG. 2 is a schematic diagram illustrating a system layout of a firstembodiment according to the present invention.

FIG. 3 is a flow chart for a fuel supply shut off control of the firstembodiment.

FIG. 4 is a flow chart for a fuel supply shut off control of a secondembodiment.

FIG. 5 is a flow chart for a fuel supply shut off control of third andfourth embodiments.

FIG. 6 is a flow chart for a fuel supply shut off control of fifth andsixth embodiments.

FIG. 7 is a flow chart for a fuel supply shut off control of a seventhembodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

As follows is a description of embodiments of the present inventionbased on the drawings. In FIG. 2 which shows a hardware layout, anintake passage 2 of an internal combustion engine 1 is fitted with athrottle valve 3 and respective fuel injection valves 4 for each of thecylinders. Also provided is a throttle sensor 5 connected to thethrottle valve 3 for detecting the valve opening thereof (this hardwarelayout is common to embodiments of the present invention).

The internal combustion engine 1 is connected to an automatictransmission 6 which incorporates a torque converter. An enginerotational speed detection sensor 7 for detecting the engine rotationalspeed is fitted to the input shaft of the torque converter, while atorque sensor 8 for detecting the torque of the output shaft of theautomatic transmission 6 is fitted to the output shaft.

Detection signals from the respective sensors are input to a controlcircuit 9 which incorporates a micro computer. The control circuit 9controls the fuel injection amount from the fuel injection valves 4 inaccordance with the operating conditions detected on the basis of thevarious signals.

Fuel supply shut off according to the present invention is carried outwith satisfaction of fuel shut off conditions such as; the rate ofclosing the throttle valve 3 in a deceleration condition exceeds apredetermined value, and the engine rotational speed at commencement ofthe deceleration operation exceeds a predetermined value.

As follows is a description of a fuel supply shut off control of a firstembodiment in accordance with the flow chart of FIG. 3.

In step 41 ("step" denoted by S in the figures) it is judged ifconditions for fuel supply shut off have occurred. That is, if the rateof closing the throttle valve 3 detected by the throttle sensor 5exceeds a predetermined value, with the engine rotational speed Ndetected by the engine rotational speed sensor 7 above a predeterminedvalue.

In step 42, it is judged if the direction of the automatic transmissionoutput shaft torque detected by the torque sensor 8 (the direction ofdriving force transmission from the engine to the automatictransmission), which is assumed positive at the time ofnon-deceleration, has changed to negative. That is, if vehicledeceleration has commenced due to rotational drive from the automatictransmission 6 of the engine 1 being a load.

When vehicle deceleration is detected with a torque change to thenegative direction, control proceeds to step 43 and the fuel supply toall cylinders of the engine 1 is shut off.

The fuel supply is subsequently reopened under conditions such as, whenthe engine rotational speed falls below a second predetermined value dueto the deceleration. Description of the reopening control is omitted.

With such a fuel supply shut off control, the fuel supply is shut offafter the deceleration operation, when an actual vehicle deceleration isdetected. Consequently, a good deceleration performance which satisfiescomfortable ride requirements is obtained, and economy is also satisfieddue to the avoidance of wasteful delay in shutting off the fuel supply.

In this embodiment, the vehicle deceleration detection step or devicecomprises the torque sensor 8 and the function of step 42, while thefuel supply shut off step or device comprises the function of step 43.

FIG. 4 shows a fuel supply shut off control according to a secondembodiment.

In step 1, as with the beforementioned step 41, it is judged ifconditions for fuel supply shut off have occurred.

If so, control proceeds to step 2 to shut off the fuel supply to some ofthe cylinders of the engine 1.

In step 3, as with the beforementioned step 42, it is judged if vehicledeceleration has commenced.

When judged that vehicle deceleration has commenced, control proceeds tostep 4 and the fuel supply to all cylinders of the engine 1 is shut off.

With such a fuel supply shut off control, the deceleration effect isincreased by a certain amount by shutting off the fuel supply to some ofthe cylinders immediately after the occurrence of fuel shut offconditions. Then the fuel supply to the remaining cylinders is timed tobe shut off with commencement of actual vehicle deceleration, withoutinfluence from conditions at the time of and after the decelerationoperation. The speed reducing force can therefore be made to act at anoptimum effective timing without an accompanying large torque change.Consequently a good deceleration performance which adequately satisfiescomfortable ride requirements is obtained, and economy is also satisfieddue to the avoidance of wasteful delay in shutting off the fuel supply.

Furthermore, with the second embodiment, the fuel supply shut offjudgement step or device comprises the function of step 1, the vehicledeceleration detection step or device comprises the torque sensor 8 andthe function of step 3, and the fuel supply shut off step or devicecomprises the functions of step 2, and step 4.

In third and fourth embodiments, in place of the torque sensor 8 thereis provided a turbine rotational speed sensor 10, as shown by the dottedline in FIG. 2, for detecting the rotational speed of the turbine outputshaft of the torque converter, or a vehicle speed sensor 11 as shown bythe chain line in FIG. 2, for detecting the rotational speed of theoutput shaft of the automatic transmission 6. As shown by the flow chartin FIG. 5 for the fuel supply shut off control, in step 13 it is judgedthat the vehicle is decelerated when the ratio of the engine rotationalspeed N_(E) to the turbine output shaft rotational speed N_(T) or to thetransmission output shaft rotational speed N_(O) falls below apredetermined value (that is, a value which is added a predeterminedamount to one or a value at non-deceleration time determined by the gearratio of the transmission).

That is to say, the third and fourth embodiments utilize the fact thatdue to slip in the torque converter at the time of vehicle deceleration,the rotational speed of the output shaft is greater than that of theengine.

With the third and fourth embodiments, the fuel supply shut offjudgement step or device comprises the function of step 11, the vehicledeceleration detection step or device comprises the engine rotationalspeed sensor 7, the turbine rotational speed sensor 10 or the vehiclespeed sensor 11, and the function of step 13, while the fuel supply shutoff step or device comprises the functions of step 12 and step 14.

The hardware in the fifth and sixth embodiments is similar to that ofthe third and fourth embodiments. However, as shown by the flow chart ofFIG. 6 for the fuel supply shut off control, in step 23 it is judgedthat the vehicle is decelerated when the engine rotational speed N_(E)has fallen below the turbine output shaft rotational speed N_(T) or thetransmission output shaft rotational speed N_(O) by a predeterminedvalue (differing according to the change gear ratio in the case ofN_(O)). A different method is used to that of the third and fourthembodiments, but with similar considerations.

With the fifth and sixth embodiments, the fuel supply shut off judgementstep or device comprises the function of step 21, the vehicledeceleration detection step or device comprises the engine rotationalspeed sensor 7, the turbine rotational speed sensor 10 or the vehiclespeed sensor 11, and the function of step 23, while the fuel supply shutoff step or device comprises the functions of step 22 and step 24.

The effects obtained by the third through sixth embodiments are similarto those of the second embodiment since only the methods of detectingvehicle deceleration are different.

FIG. 7 shows a flow chart for a fuel supply shut off control of aseventh embodiment.

With the seventh embodiment, in step 31, it is judged if a set periodhas elapsed from commencement of a deceleration operation determined forexample by the rate of reducing the opening of the throttle valve 3.After the elapse of the set period, then in step 32 it is judged ifconditions for fuel supply shut off have occurred. If so, controlproceeds to step 33 to shut off the fuel supply to some of thecylinders. Then in step 34, vehicle deceleration is judged. Whendeceleration is judged, the fuel supply to the remaining cylinders isshut off. The judgement of vehicle deceleration in step 34 may involveany of the methods illustrated in the previous embodiments.

With the seventh embodiment, there is a first torque reduction due to areduction in fuel supply quantity at the time of the decelerationoperation. Then there is a second torque reduction due to the fuelsupply shut off to some of the cylinders after a set period. Finallythere is a third torque reduction due to the fuel supply shut off to theremaining cylinders when vehicle deceleration is detected. Since thereduction in torque is carried out in three stages, there is a gentlechange in torque, with the final fuel supply shut off to all of thecylinders being effected at an optimum timing. Hence, a gooddeceleration performance is obtained with an improvement in comfortableride and fuel consumption.

In the seventh embodiment, the fuel supply shut off judgement step ofdevice comprises the function of step 32, the vehicle decelerationdetection step or device comprises the function of step 34 and thevarious sensors used in judging the in vehicle deceleration in step 34,while the fuel supply shut off step or device comprises the functions ofstep 33, and step 35.

With the present invention as described above, the construction is suchthat the fuel supply to the engine is timed to be shut off after thevehicle deceleration operation, at the time of an actual vehicledeceleration. Consequently the deceleration function can be made to workeffectively without an accompanying large change in torque, so thatdeceleration performance can be maximized with an improvement incomfortable ride and fuel consumption.

INDUSTRIAL APPLICABILITY

The above described method and apparatus for controlling the fuel supplyshut off to an internal combustion engine according to the presentinvention enables an improvement in vehicle ride comfort and economy.Thus, the method and apparatus according to the present invention notonly give but contributes to the automotive industry.

The claims defining the invention are as follows:
 1. A method forcontrolling a fuel supply shut off of an internal combustion engine atthe time of a predetermined deceleration said method comprising thesteps of:a vehicle deceleration detection step for detecting a vehicledeceleration condition which occurs with a delay after a decelerationoperation of a driver, and a fuel supply shut off step for shutting offof the fuel supply to the internal combustion engine when a vehicledeceleration is detected by said vehicle deceleration detection step,wherein said vehicle is fitted with an automatic transmission, and saidvehicle deceleration step judges a deceleration condition when adirection of torque in an output shaft of said automatic transmissionchanges to a direction opposite to that occurring at a time ofnon-deceleration.
 2. A method for controlling a fuel supply shut off ofan internal combustion engine at the time of a predetermineddeceleration, said method comprising the steps of:a vehicle decelerationdetection step for detecting a vehicle deceleration condition whichoccurs with a delay after a deceleration operation of a driver, and afuel supply shut off step for shutting off of the fuel supply to theinternal combustion engine when a vehicle deceleration is detected bysaid vehicle deceleration detection step, wherein said vehicle is fittedwith an automatic transmission incorporating a torque converter, andsaid vehicle deceleration detection step detects a decelerationcondition on the basis of the magnitude of a rotational speed No of aninput shaft of said torque converter and the magnitude of a rotationalspeed Ne of an output shaft of said automatic transmission.
 3. A methodfor controlling a fuel supply shut off of an internal combustion engineat the time of a predetermined deceleration, said method comprising: avehicle deceleration detection step for detecting a vehicle decelerationcondition which occurs with a delay after a deceleration operation of adriver, a fuel supply shut off judgement step for judging if fuel supplyshut off is possible, and a fuel supply shut off step for shutting offthe fuel supply to some of the cylinders when it is judged by the fuelsupply shut off judgement step that fuel supply shut off is possible,and for shutting off of the fuel supply to the remaining cylinders whena vehicle deceleration is detected by said vehicle decelerationdetection step.
 4. An apparatus for controlling a fuel supply shut offof an internal combustion engine at the time of a predetermineddeceleration, said apparatus comprising:vehicle deceleration detectionmeans for detecting a vehicle deceleration condition which occurs with adelay after a deceleration operation of a driver, and fuel supply, shutoff means for shutting off of the fuel supply to the internal combustionengine when a vehicle deceleration is detected by said vehicledeceleration detection means, wherein said vehicle is fitted with anautomatic transmission, and said vehicle deceleration detection meansjudges a deceleration condition when a direction of torque in an outputshaft of said automatic transmission changes to a direction opposite tothat occurring at a time of non-deceleration.
 5. An apparatus forcontrolling a fuel supply shut off of an internal combustion engine atthe time of a predetermined deceleration said apparatuscomprising:vehicle deceleration detection means for detecting a vehicledecelerating condition which occurs with a delay after a decelerationoperation of a driver, and fuel supply shut off means for shutting offof the fuel supply to the internal combustion engine when a vehicledeceleration is detected by said vehicle deceleration detection means,wherein said vehicle is fitted with an automatic transmissionincorporating a torque converter, and said vehicle decelerationdetection means detects a deceleration condition on the basis of themagnitude of a rotational speed No of an input shaft of said torqueconverter and the magnitude of a rotational speed Ne of an output shaftof said automatic transmission.
 6. An apparatus for controlling a fuelsupply shut off of an internal combustion engine at the time of apredetermined deceleration, said apparatus comprising: vehicledeceleration detection means for detecting a vehicle decelerationcondition which occurs with a delay after a deceleration operation of adriver, fuel supply shut off judgement means for judging if fuel supplyshut off is possible, and fuel supply shut off means for shutting offthe fuel supply to some of the cylinders when it is judged by the fuelsupply shut off judgement means that fuel supply shut off is possible,and for shutting off of the fuel supply to the remaining cylinders whena vehicle deceleration is detected by said vehicle decelerationdetection means.